In purely gameplay terms, you've nailed it. There is no in game advantage to wearing metal armor over leather, though there is a (very slight) disadvantage in that you're more limited in who you can initiate grapples with.

That said, metal armor tends to be heavier (though not always). We generally don't see plate very much. The two most common armor types are chain and leather. Leather is (generally) lighter, but chain breathes better. It really comes down to an aesthetic choice for most people.

_________________- Derian -

"An octopus has eight arms, three hearts, five *, two Super Bowl rings, a beak, and the power to solve crimes."